Artificial hair fiber and hairpiece product

ABSTRACT

An artificial hair fiber is provided that is easy to curl or set. An artificial hair fiber is usually formed and processed within a temperature range from 90 to 150° C. The artificial hair fiber has a storage elastic modulus E′ in the formation temperature range. A ratio (E′ 90 /E′ 150 ) of a storage elastic modulus E′ at a temperature of 90° C. to a storage elastic modulus E′ at a temperature of 150° C. is 3 to 20. By this means, the artificial hair fiber can be well curled or transformed, maintaining a desired dynamic characteristic without being melted. The artificial hair fiber can be formed and processed into such a curled hair, so that it is possible to provide a hairpiece product that meets the fashion needs of users.

TECHNICAL FIELD

The present invention relates to artificial hair fiber and a hairpiece product using the same.

TECHNICAL BACKGROUND

Conventionally, to manufacture hairpiece products such as hair wigs, artificial hair made of synthetic fibers has been used. Although most of the artificial hair is originally straight, there is an increasing demand for artificial hair fiber that can be processed into, for example, curled hair, due to an increase in the uses for fashion purposes.

As artificial hair fiber that easy to curl and set, there has been known, for example, flame resistant polyester artificial hair fiber (see Patent Document 1). This artificial hair fiber has high heat resistance, and therefore can be heated at a high temperature of a hair iron and the like, and can be well curled.

However, most of the manufacturers of the hairpiece products curl the fiber at a temperature from 90 to 150° C. that is lower than the temperature of the hair iron in order to prevent heat damage. Therefore, there has been a problem that the artificial hair fiber made of the above-described flame resistant polyester cannot be well curled.

PRIOR ART DOCUMENT

-   Patent Document 1: Japanese Patent Application Publication No.     2009-235626

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide artificial hair fiber that can be easily processed into, for example, curled hair.

The present invention provides artificial hair fiber and a product manufactured by using the artificial hair fiber. The artificial hair fiber according to the present invention has a storage elastic modulus E′, a ratio (E′₉₀/E′₁₅₀) of a storage elastic modulus E′ at a temperature of 90° C. to a storage elastic modulus E′ at a temperature of 150° C. is 3 to 20.

Here, a curve of the storage elastic modulus E′ includes a glass state range in which the storage elastic modulus E′ is constant and a transition range in which a change rate in the storage elastic modulus E′ becomes maximum, the transition range being on a higher temperature side than the glass state range. Preferably, a temperature coordinate of an intersection at which a tangent line of a curve of the storage elastic modulus E′ passing through the glass state range intersects a tangent line of a curve of the storage elastic modulus E′ passing through the transition range is located between 180 to 240° C.

More preferably, the artificial hair fiber is made of a resin composition primarily consisting of one or both of thermoplastic polyester resin and thermoplastic polyamide resin.

Further, the artificial hair fiber is manufactured by melting and discharging the resin composition from a nozzle hole to produce an un-stretched yarn, and applying a stretching process to the un-stretched yarn. Preferably, a ratio (D₁/D₂) of a stretch D₁ while the un-stretched yarn is produced after the resin composition is melted and discharged to a stretch D₂ during the stretching process is 1.5 to 14.0.

It is possible to manufacture a hairpiece product by using the above-described artificial hair fiber.

According to the present invention, it is possible to provide an artificial hair fiber that can be easily processed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graph showing the relationship between storage elastic modulus and temperature;

FIG. 2 is a graph showing the viscoelasticity of artificial hair fiber according to examples; and

FIG. 3 is a graph showing the viscoelasticity of artificial hair fiber according to comparative examples.

DESCRIPTION OF EMBODIMENTS

Hereinafter, although the present invention will be described in detail, it is noted that the present invention is not limited to the following embodiments.

The present invention provides artificial hair fiber that can be well curled (set, or styled). The artificial hair fiber should not be limited to those described above, but may be, for example, synthetic fiber obtained by spinning resin composition, or fiber obtained by applying a processing agent to the synthetic fiber.

Formation and processing the artificial hair fiber may be done by an artificial hair fiber manufacturer, a person who processes the fiber into a hairpiece product and a user who bought the product. For example, a manufacturer of artificial hair fiber or hairpiece product may form and process the artificial hair fiber to have it curled before the artificial hair fiber is put on sale. The formation and processing may be done any time, before, during or after the processing of the artificial hair fiber into a hairpiece product. Here, the formation and processing are not limited to curling (waving), but straightening the curled hair may also be applicable.

Methods of forming the artificial hair fiber should not be limited. There are various methods, for example, a method of placing a heating device such as a hair iron in contact with the artificial hair fiber or pressing the artificial hair fiber with the hair iron; a method of exposing the artificial hair fiber wound around a core (metal cylinder) to heated air; and a method of heating the core around which the artificial hair fiber is wound. In general, it is usual to use a method of placing a core wound by the artificial hair fiber in a heating oven and heating the core.

A heating temperature (formation temperature) in the formation process should not be specifically limited. Although the heating temperature can be changed depending upon the raw materials of the artificial hair fiber, the formation temperature may be in a range from 90 to 150° C. in general.

FIG. 1 is a schematic diagram explaining the viscoelasticity of the artificial hair fiber. Both storage elastic modulus E′ and loss elastic modulus E″ of synthetic fiber will drop upon being heated. Here, a higher change rate in these elastic modulus will cause an easier transformation (such as a curling) of the synthetic fiber. Therefore, a suitable synthetic fiber for manufacturing the artificial hair fiber is the one whose elastic moduli significantly changes within its formation temperature range (temperature range for curling in an oven shown in FIG. 1) when curling.

Curve “c” in FIG. 1 shows a change in the elastic moduli (E′, E″) of heat-resistant artificial hair that is commercially available. The change rate in the elastic moduli (E′, E″) of the heat-resistant artificial hair is small within the formation temperature range due to its heat resistance, so that a formation such as curling is not acceptable. Meanwhile, as shown by curves “a” and “b” in FIG. 1, when the change rate in the elastic moduli (E′, E″) is large within the formation temperature range, the artificial hair can be easily transformed, thereby obtaining an acceptable formability.

It is possible to control a change in the elastic moduli (E′, E″) within the formation temperature range by changing the blending ratio of the resin composition which is a raw material for manufacturing the artificial hair fiber. For example, if thermoplastic resin with a low glass-transition temperature is used as the main raw material, it is possible to significantly change the elastic moduli (E′, E″) within the formation temperature range, but the heat resistance is reduced.

After a forming process and purchased by a user, a hairpiece product may be processed by the user to satisfy the his or her taste (hereinafter referred to as “post-formation”). Commercially available heating devices (e.g. a hair iron) are often used for the post-formation processing. Although the heating temperatures of those heating devices are within a wide range from 60 to 240° C., the temperature of the post-formation tends to be higher (180 to 240° C.) than the formation temperature before the product is sold in the market, since users prefer to set the hairpiece product well in a short time.

As shown by curve “b”, even if the change rate of the temperature within the formation temperature range is large, there is still a possibility that the fiber will be melted and transformed before the temperature reaches the post-formation temperature range (temperature range for curling with iron in FIG. 1). As a result, the fiber cannot tolerate the high temperature of the hair iron, and therefore is likely to significantly shrink, be damaged and broken.

Therefore, as shown by curve “a”, it is most preferable that the fiber does not melt before the temperature reaches the post-formation temperature range and the rate of change is large in the formation temperature range and also in the post-formation temperature range. Here, the elastic moduli (E′, E″) significantly changes during the melting. Here, “a” and “c” in FIG. 1 melt in the post-formation temperature range, but “b” melts before the post-formation temperature range. In normal use, the artificial hair fiber is not heated at a high temperature above the post-formation temperature range. Therefore, if the rate of change is large in the post-formation temperature range, the fiber is allowed to melt in the post-formation temperature range, as shown by “a” and “c”.

The formation temperature that is widely adopted in the artificial hair field is within 90 to 150° C., while the post-formation temperature that the users prefer is within 180 to 240° C. Therefore, it is preferable that the elastic moduli significantly change in both these ranges.

When a change in the elastic moduli increases, the fiber can be well curled. However, if the change is too large, the fiber shrinks. For example, it is preferred that a ratio of a storage elastic modulus E′ at 90° C. to a storage elastic modulus E′ at 150° C. E′₉₀/E′₁₅₀ be 3 to 20, and more preferably 4 to 10. If E′₉₀/E′₁₅₀ is lower than 3, a change in the elastic moduli will be small in the formation temperature range (90 to 150° C.), and therefore it is difficult to curl the fiber well. On the other hand, if E′₉₀/E′₁₅₀ is higher than 20, the fiber shrinks and therefore it is also difficult to curl the fiber well. If E′₉₀/E′₁₅₀ is 4 to 10, it is possible to curl the fiber very well without shrinking, and therefore this temperature range is particularly preferable.

In addition, taking into account the post-formation (curling with an iron), it is preferable for the fiber to have a high heat resistance. However, if the heat resistance is too high, it is not possible to perform the post-formation with an iron, and therefore it is preferred that a transformation temperature at which a crystal glass state collapses is within 180 to 240° C. Here, the transformation temperature may be defined as an intersection at which a tangent line passing through the glass state range having a constant storage elastic modulus is intersecting a tangent line passing through the transition range (or transition point) on a higher temperature side than the glass state range, which has a maximum change rate in storage elastic modulus.

The artificial hair fiber that meets the above-described requirements including the temperature and the viscoelasticity can be produced by appropriately adjusting the manufacturing conditions of the fiber and the blending ratio of the raw materials.

<Resin Composition>

The resin composition consists primarily of thermoplastic resin (50% by mass or more) and contains additives such as a flame retardant, filler, a coloring agent and antioxidant. The viscoelasticity (such as E′ and E″) can be adjusted by changing a mixing ratio of two or more kinds of thermoplastic resin, or a mixing ratio of thermoplastic resin and additives (a flame retardant, filler and the like). Particularly, by combining two or more kinds of thermoplastic resin having different glass-transition temperatures, it is possible to produce an artificial hair fiber whose elasticity significantly changes in both the formation temperature range and the post-formation temperature range.

In addition, it is possible to adjust the viscoelasticity by adjusting the manufacturing conditions of the fiber. For example, it is possible to control the viscoelasticity by changing the draw ratio and the stretch ratio appropriately. Here, the draw ratio means a ratio for the drawing of the fiber after being discharged from the nozzle hole until being cooled. Meanwhile, the stretch ratio means a ratio for the stretching of an un-stretched yarn (a magnification for a yarn to be stretched)

Hereinafter, the draw ratio and the stretch ratio will be described in detail below. The manufacturing process of the artificial hair fiber includes the steps of: heating and melting a composition containing thermoplastic resin; discharging the melted composition from the nozzle hole; (if necessary) passing the composition through a heating sleeve; and cooling it to obtain an un-stretched yarn. The draw ratio means a ratio for the drawing of the fiber after the fiber is discharged from the nozzle until being cooled and becoming an un-stretched yarn. Here, the ratio for the drawing can be calculated based on a ratio of a speed at which the un-stretched yarn is taken up to a speed at which the fiber is discharged from the nozzle.

The un-stretched yarn is subjected to a stretching process in order to improve the tensile strength of the fiber. In the stretching process, the un-stretched yarn once having been cooled is stretched while being heated at a lower temperature than the heating and melting temperature when the yarn is produced. Here, the stretch ratio means a ratio for the stretching of the un-stretched yarn (before being heated and stretched) until being stretched. This stretch ratio can be calculated based on a ratio of a speed at which the un-stretched yarn is wound off to a speed at which the stretched yarn is wound up.

<Thermoplastic Resin>

The thermoplastic resin should not be limited in use, and it is possible to use vinyl chloride resin, acrylic resin, polypropylene resin, polylactic resin, polyester resin, polyamide resin and the like. However, when only a resin with a low heat resistance, such as vinyl chloride resin, is used, the fiber will be damaged in the post-formation under a high temperature (180° C. or higher). Therefore, it is preferred that heat resistant resin such as polyamide resin and polyester resin is used independently or in combination.

Among the above-described resins, the present invention prefers to use a polyamide fiber primarily consisting of polyamide resin and a polyester fiber primarily consisting of polyester resin, since they are easy to process and have a desired strength.

It is preferred that the polyamide fiber or the polyester fiber is made of a composition obtained by mixing 5 to 30 parts by weight of phosphorous or bromine flame retardant and 100 parts by weight of polyamide resin (or polyester resin) and melt-kneading them. In this case, the flame resistance can be significantly improved by combining the resin and a certain percentage of a phosphorous or bromine flame retardant.

The polyamide resin used for the polyamide fiber should not be limited, but it is preferable to use at least one kind of resin selected from a group consisting of, for example, nylon 6; nylon 6,6; nylon 4,6; nylon 12; nylon 6,10; and nylon 6,12, and among them, nylon 6,6 is most preferable. When the nylon 6,6 is employed, the texture is particularly acceptable. The weight-average molecular weight (Mw) of the polyamide may be a value within a range from ten thousands to two hundred thousands, and to be more specific, may be ten thousand, twenty thousand, forty thousand, sixty thousand, eighty thousand, one hundred thousand, one hundred fifty thousand and two hundred thousand.

The kind of the polyester resin used for the polyester fiber should not be limited, it is possible to use polyethylene terephthalate, polyphenylene ether, polypropylene terephthalate, and polybutylene terephthalate. Among them, the polyethylene terephthalate is most preferable in view of the heat resistance.

The kind of the phosphorous flame retardant should not be limited, and it is possible to employ a generally used phosphorous flame retardant. To be more specific, it is possible to use a phosphate compound, a phosphonate compound, a phosphinate compound, a phosphine oxide compound, a phosphonite compound, a phosphinite compound and a phosphine compound. These compounds may be independently used, or two or more kinds of the compounds may be used together.

In addition, the kinds of bromine flame retardant should not be limited, either. It is possible to employ a generally used bromine flame retardant. To be more specific, it is possible to use a bromine-containing phosphate ester flame retardant, such as pentabromotoluene, hexabromobenzene, decabromodiphenyl, decabromodiphenyl ether, bis(tribromophenoxy)ethane, tetrabromophtalic anhydride, ethylenebis(tetrabromophthalimide), ethylenebis(pentabromophenyl), octabromotrimethylphenylindane, and tris(tribromoneopentyl)phosphate; a brominated polystyrene flame retardant; a brominated poly(benzyl acrylate) flame retardant; a brominated epoxy flame retardant; a brominated phenoxy flame retardant; a brominated polycarbonate flame retardant; a bromine-containing triazine compound such as tetrabromobisphenol A, tetrabromobisphenol A-bis(2,3-dibromopropyl ether), tetrabromobisphenol A-bis(allylether), tetrabromobisphenol A-bis(hydroxyethyl ether), tetrabromobisphenol A derivatives, and tris(tribromophenoxy)triazine; and isocyanuric acid compound such as tris(2,3-dibromopropyl) isocyanurate. They may be used alone, or in a combination of two or more of them.

It is preferred that the content of the above-described phosphorous or bromine flame retardant is 5 to 30 parts by weight for 100 parts by weight of polyamide (polyester), and more preferably is 5 to 20 parts by weight. Within these ranges, it is possible to ensure a sufficient flame resistance and to prevent various physical properties from deteriorating.

Moreover, 0.1 to 5 parts by weight of fine particles may be contained in 100 parts by weight of polyamide resin (or polyester resin). When the fine particles are contained in this ratio, the following advantageous can be provided. Namely, it is possible to improve the gloss or luster of the fiber surface by forming an uneven fiber surface, thereby increasing the fiber surface area and thus producing an improved hygroscopic property for the fiber. The ratio of the fine particles to 100 parts of the polyamide resin is preferably 0.2 to 3 parts by weight, and more preferably 0.2 to 2 parts by weight. This ratio can allow the above-described effect to be significant.

The average size of the fine particles is preferably 0.1 to 15 μm, more preferably 0.2 to 10 μm, and further more preferably 0.5 to 8 μm.

Within these ranges, it is possible to provide a sufficient effect of adjusting the gloss or luster and to prevent the fiber strength from decreasing, which is possibly caused due to the addition of the fine particles.

The above-described fine particles may be organic, or inorganic, or may include both organic and inorganic fine particles. The kinds of organic fine particles should not be limited as long as at least part of them is not compatible with the polyamide or polyester resin, and for example, fine particles made of cross-linked acrylic resin or cross-linked polyester resin are applicable.

The above-described cross-linked acrylic particles may be obtained by dispersing acrylic monomers and a crosslinking agent in water, followed by crosslinking and curing. Here, the acrylic monomer used herein may include an acrylic acid and its derivatives, such as methyl acrylate, butyl acrylate, hexyl acrylate, cyclohexyl acrylate, hydroxyethyl acrylate, acrylonitrile, acrylamide and N-methylolacrylamide. Alternatively, it is also possible to use a methacrylic acid and its derivatives. The derivatives may include methyl methacrylate, butyl methacrylate, hexyl methacrylate, glycidyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, N-vinyl-2-pyrrolidone methacrylate, methacrylonitrile, methacrylamide, N-methylolmetacrylamide, 2-hydroxyethyl methacrylate, with each molecule having one vinyl group, thus forming a vinyl monomer. These monomers may be used individually, or two or more kinds of these monomers may be used in combination.

The above-described cross-linked polyester particles may be obtained by dispersing unsaturated polyester and vinyl monomers in water and crosslinking and curing them. The kind of unsaturated polyester used herein should not be limited. The unsaturated polyester may be obtained, for example, by polymerizing an α,β-unsaturated acid or the mixture of the α,β-unsaturated acid and a saturated acid with dihydric alcohol or triatomic alcohol. The unsaturated acid may include, for example, a fumaric acid, a maleic acid and an itaconic acid. Meanwhile, the saturated acid may include, for example, phthalic acid, terephthalic acid, succinic acid, glutaric acid, tetrahydrophthalic acid, adipic acid and sebacic acid. The dihydric alcohol and the triatomic alcohol may include, for example, ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, 1,3-propanediol, 1,6-hexanediol and trimethylolpropane. Meanwhile, the kind of vinyl monomer should not be limited, but may include, for example, styrene, chlorostyrene, vinyltoluene, divinylbenzene, acrylic acid, methylacrylate, acrylonitrile, ethylacrylate, and diallylphthalate.

The above-described crosslinking agent is not limited in use as long as it is a monomer that is a molecule having two or more vinyl groups, and more preferably, a monomer is a molecule having two vinyl groups. A monomer used as a crosslinking agent should not be limited in use, but includes, for example, divinylbenzene, and a reaction product of glycol with methacrylic acid or acrylic acid, such as ethylene glycol dimethacrylate and neopentyl glycol dimethacrylate. It is preferred that an amount of the crosslinking agent is 0.02 to 5 parts by weight for 100 parts by weight of the acrylic monomer. As a polymerization initiator, it is preferable to use a peroxide radical polymerization initiator. For example, a peroxide radical polymerization initiator may include, a benzoyl peroxide, 2-ethylhexyl perbenzoic acid, di-tert-butyl peroxide, cumene hydroperoxide and methyl ethyl ketone peroxide. It is preferred that an amount of the radical polymerization initiator is 0.05 to 10 parts by weight for 100 parts by weight of the acrylic monomer.

As the above-described inorganic fine particles, it is preferable to have an index of refraction similar to that of polyamide and/or a phosphorous-containing flame retardant, in view of an influence on the transparency and the color development of the fiber. For example, it is possible to use calcium carbonate, silicon oxide, titanium oxide, aluminium oxide, zinc oxide, talc, kaolin, montmorillonite, bentonite and mica.

In addition to the above-described fine particles and flame retardants, it is also possible to contain a flame retardant an auxiliary agent, a heat resisting agent, a light stabilizer, a fluorescent agent, an oxidation inhibitor, an antistatic agent, a plasticizer, a lubricant and a resin other than thermoplastic resin. By containing a coloring agent such as pigment, it is possible to produce pre-colored fiber (so-called “spun-dyed fiber”).

<Manufacturing Process>

Next, an explanation will be given to an exemplary process for manufacturing synthetic fiber. However, the present invention should not be limited by this.

The above-described additives such as a flame retardant and particles are dry-blended into thermoplastic resin such as polyamide or polyester resin in a predetermined proportion in advance, and then melt-kneaded by using a kneading machine. Various commonly used kneading machines may be employed as a melt-kneading apparatus. For example, it is possible to use a single-screw extruder, a twin-screw extruder, a roll, a Banbury mixer, and a kneader as a melt-kneading apparatus. Among them, a twin-screw extruder is preferable, since it is easy to adjust a kneading degree and easy to operate. The kneaded material obtained by the melt-kneading is melt-spun to produce a spun yarn.

For example, the kneaded material is melted in a melt-spinning device such as an extruder, a gear pump and a pipe sleeve, under a temperature of 27 to 310° C. Then, the kneaded material is passed through a heating sleeve, cooled to a glass-transition temperature or lower, and taken out at a speed of 50 to 5000 m/min, thereby producing a spun yarn. In addition, the yarn may be cooled with cooling water in a water tank to control the fineness. It is possible to appropriately control the temperature and the length of the heating sleeve, the temperature and the blast volume of a cooling air machine, the temperature of the cooling water tank, the cooling time and the take-up speed, according to the discharge quantity and the number of the holes of the pipe sleeve.

During the melt spinning, the cross-section of the artificial hair fiber may be formed into a cocoon shape, a Y-shape, an H-shape and an X-shape by using a spinning nozzle with a specially-shaped nozzle hole.

The obtained un-stretched yarn is subjected to a hot stretching process in order to improve the tensile strength of the fiber. The hot stretching process may be performed by a two-step method or a direct stretching method. The two-step method includes the steps of: winding an un-stretched yarn around a bobbin once; and stretching the yarn in a different step from a melt spinning step. The direct stretching method includes stretching the un-stretched yarn following the melt spinning step without winding the un-stretched yarn around the bobbin. In addition, the hot stretching process may be performed by a one-step stretching method or a multistep stretching method. In the one-step stretching method, the yarn is stretched to a desired stretch ratio in one step. In the multistep stretching method, the yarn is stretched two or more times to reach the desired stretch ratio. As heating means in the hot stretching process, it is possible to use a heating roller, a heat plate, a steam jet device and a warm water tank, alone or in combination.

As the fineness of the synthetic fiber, 30 to 80 dtex, and preferably 35 to 75 dtex is suitable to be used for artificial hair.

Among synthetic fibers, a polyamide fiber is a non-crimped silk fiber, and its fineness is usually 10 to 100 dtex, preferably 30 to 80 dtex, and more preferably 35 to 75 dtex.

<Post-Processing>

Although the produced synthetic fiber may be used as an artificial hair fiber as it is, its texture may be improved by coating it with a treatment agent containing an oil such as silicone oil. A coating with a treatment agent may be done at any time, before, during and after processing the synthetic fiber into a hairpiece product. Here, in view of a working efficiency for a uniform coating, a coating during the process for processing the synthetic fiber into a hairpiece product is most preferable.

The artificial hair fiber may not only be used alone for a hairpiece product (headdress product), but also used in combination with human hair or other artificial hairs.

The hairpiece product may include a wig, a hairpiece, a blade, a hair extension, doll's hair and the like. The use of the artificial hair fiber should not be limited. In addition to a hairpiece product, the artificial hair fiber of the present invention may also be used for false beard, false eyelash, false eyebrow and the like.

Examples

Now, although examples of the present invention will be described in detail below, it is noted that the present invention is not limited to the examples.

<Manufacturing Process>

Hereinafter, a method of manufacturing a hair fiber bundle will be described in the following examples.

The polyamide (or polyester) fiber was produced by the following method. First, polyamide (or polyester) resin, phosphorous or bromine flame retardant and fine particles, all used as raw materials here, were dried to reduce their moisture content to 100 ppm or lower.

The raw materials used were as follows.

Nylon 6: Ube Industries, Ltd. 1013B

Nylon 6,6: Toray Industries, Inc. CM3001-N Phosphorous flame retardant:

DAIHACHI CHEMICAL INDUSTRY CO., LTD. PX-200

Bromine flame retardant: ALBEMARLE JAPAN CORPORATION, HP-7010 Fine particles: cross-linked acrylic particles 1.8 μm, Soken Chemical & Engineering Co., Ltd.

Polyester (PET): Mitsubishi Chemical Corporation, BK-2180

The blending ratios (mass ratio) of the materials are represented in the following table 1.

TABLE 1 Comp. Comp. Ex 1 Ex 2 Ex 3 Ex 4 Ex 1 Ex 2 Nylon 6 — — — 80 — — Nylon 6,6 — 100  — 20 100  100  Polyester 100  — 100  — — — Phosphorous flame — — — — — — retardant Bromine flame retardant 15 15 15 15 15 15 Fine particles  1  1  1  1  1  1 Ex: Example Com. Ex: Comparative example

Next, predetermined amounts of colored pellets were added to the above-described dried materials, and the materials were dry-blended in the percentages shown in table 1.

The dry-blended material was melt-kneaded at a temperature of 280° C. Then, the melt-kneaded material was formed into pellets.

The melt-kneading and the pellet-formation were performed by the twin-screw extruder.

These pellets were dried to reduce the moisture content to 100 ppm or lower, and then formed into an un-stretched yarn in a melt-spinning machine. To be more specific, the nozzle hole of the melt spinning machine has a circular cross section and is 0.5 mm in size. Melted polymer pellets were discharged from the nozzle hole of the melt spinning machine at a temperature of 280° C. Then, the discharged melted polymer was cooled in the water tank (located 30 mm below the nozzle hole) at a temperature of 50° C., followed by being taken-up and wounded. In this way, an un-stretched yarn is produced. The draw ratio was controlled by changing the speed at which the un-stretched yarn was wounded.

Next, the produced un-stretched yarn was stretched to a length which is 4 times as long as the original length, and then is subjected to heat treatment. Then, the stretched yarn is wound at a speed of 30 m/min to produce a fiber primarily consisting of polyamide (or polyester). In the stretching and the heat treatment of the un-stretched yarn, a heat roller heated to 85° C. and 200° C., respectively, is used.

By this means, the fibers in examples 1 to 4 and comparative examples 1 to 2 were obtained. Here, the stretch ratio was controlled by changing the speed at which the un-stretched yarn was wound off.

The following tests were conducted to valuate the fibers obtained in examples 1 to 4 and comparative examples 1 and 2.

<Degree of Curling in Oven>

To evaluate the degree of curling in oven, a fiber bundle (length: 50 cm) was wound around an aluminum cylinder (diameter: 20 mmφ); each end of the fiber bundle was fixed to the aluminum cylinder; and the fiber bundle was put in an air-circulated oven at a temperature of 100° C. and heated for 30 minutes.

Next, the aluminum cylinder around which the fiber bundle was wound was left in a thermostatic chamber for 24 hours. Here, the temperature in the thermostatic chamber is 23° C. and the relative humidity is 50%.

After that, the fiber bundle was removed from the aluminum cylinder and suspended, with its one end fixed.

The degree of curling was evaluated based on a value obtained by dividing the curled fiber length from its root to the tip with the entire length (50 cm) of the un-curled fiber. The smaller the value, the greater the degree of curling.

Evaluation criteria were as follows, and A and B were acceptable values in the evaluation.

A: lower than 0.75

B: 0.75 or higher and lower than 0.85

C: 0.85 or higher

<Processability>

To evaluate processability, the frequency of the yarn break during the fiber manufacturing process (spinning and stretching) was checked, and evaluated by the following criteria.

A and B are acceptable values in the evaluation.

A: no yarn break;

B: yarn break occurs about every 30 minutes, but there is no problem on the quality of the product; and

C: there is a lot of yarn break and it is difficult to manufacture a product.

<Physical Property>

In accordance with JIS-L1069, ten pieces of the fiber were randomly selected and subjected to a tensile test to calculate an average tensile strength value. The test was conducted under the following conditions: test temperature is 23° C.; relative humidity is 50%; tensile speed 200 mm/min; and an clearance (distance between chucks) is 20 mm.

Evaluation criteria were as follows:

A: tensile strength (cN/dtex) was 1.0 or higher and 2.0 or lower B: tensile strength (cN/dtex) was 0.5 or higher and 3.0 or lower C: tensile strength (cN/dtex) was lower than 0.5 or higher than 3.0 A: quite acceptable B: acceptable C: not acceptable

<Dynamic Viscoelasticity>

Dynamic viscoelasticity (stretch modulus) was measured under the following conditions: frequency is 1.0 Hz; initial temperature is 30° C.; final temperature is 260° C.; and rate of temperature increase is 2° C./min. The measuring equipment used in the measurement was DMS6100, which was available from SII Nanotechnology Inc. During the measurement, a bundle of forty pieces of fiber was sandwiched between the chucks with the chuck distance being 3 mm.

The results of the measurement are shown in table 2 together with manufacturing conditions such as kinds of resin, draw ratio, stretch ratio and the like.

TABLE 2 Ex Comp. Ex 1 2 3 4 5 6 1 2 Storage elastic modulus 8.2 3.8 10.4 5.3 3.6 18.5 2.0 34 ratio (E₉₀/E₁₅₀) Resin PET PA66 PET PA66/PA6 PET PA66 PA66 PA66 Nozzle hole diameter (mm) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Draw ratio (times) 9 9 12 9 6 18 5 25 Stretch ratio (times) 3 3 2 3 4 1.5 5 1.5 Draw ratio/stretch ratio 3 3 6 3 1.5 12 1 16.7 Fineness (dtex) 70 70 80 70 80 70 76 58 Degree of curling in oven A B B A B B C C Processability A A A A B A B B Physical property A A B A A B B C (tensile strength)

In examples 1 to 4, the ratio of draw ratio D1 to stretch ratio D2 was 1.5 to 14.0, and the storage elastic modulus ratio (E′₉₀/E′₁₅₀) was 3 to 20. Here, not only the degree of curling in oven and the processability, but also strength was excellent. Among them, examples 1 and 4 in which the storage elastic modulus ratios (E′₉₀/E′₁₅₀) were 4 to 10 yield good results of the degree of curling in oven.

When the ratio (D₁/D₂) of the draw ratio D₁ to the stretch ratio D₂ was smaller than 1.5, the un-stretched yarn will be excessively stretched and therefore likely to be broken during the stretching, so that the processability tended to be worse. On the other hand, when the ratio (D₁/D₂) of the draw ratio D₁ to the stretch ratio D₂ was greater than 14.0, the un-stretched yarn will not be sufficiently stretched, so that the tensile strength was likely to decrease.

In example 5, the storage elastic modulus ratio (E′₉₀/E′₁₅₀) was 3.6 and the degree of curling in oven and the processability were not A, but B. This result was within an acceptable range. Further, in example 5, the ratio (D₁/D₂) of the draw ratio D₁ to the stretch ratio D₂ was 1.5, and the processability was B. This result was also within an acceptable range.

In example 6, the storage elastic modulus ratio (E′₉₀/E′₁₅₀) was 18.5 and the degree of curling in oven and the physical property (tensile strength) was not A, but B. This result was also within an acceptable range. In addition, in example 6, the ratio (D₁/D₂) of the draw ratio D₁ to the stretch ratio D₂ was 12, and the tensile strength (physical property) was B. This result was also within an acceptable range.

In contrast, in comparative example 1 the storage elastic modulus ratio (E′₉₀/E′₁₅₀) was smaller than 3 and the degree of curling in oven was C, and, in comparative example 2 in which the storage elastic modulus ratio (E′₉₀/E′₁₅₀) was greater than 20, not only the degree of curling in oven but also the tensile strength was C.

FIG. 2 shows the result of the measurement of the dynamic viscoelasticity in example 1. FIG. 3 shows the result of the measurement of the dynamic viscoelasticity in comparative example 1. As seen from FIG. 3, it was found that the artificial hair fiber of comparative example 1 was not melted even at a high temperature of 240° C., and the storage elastic modulus E′ was maintained, exhibiting a high heat resistance. However, since the heat resistance was too high, the artificial hair fiber was not melted in the formation temperature range (90 to 150° C.), nor in the post-formation temperature range (180 to 240° C.), and both the storage elastic modulus E′ and the loss elastic modulus E″ changed little. In contrast, with the artificial hair fiber of example 1, it was found that the storage elastic modulus E′ and the loss elastic modulus E″ significantly changed in both the formation temperature range and in the post-formation temperature range, and the formability is excellent.

M₁ shown in FIGS. 2 and 3 is a tangent line of the curve of the storage elastic modulus E′, which passes through the glass state range in which the curve is flat. M₂ is a tangent line of the curve of the storage elastic modulus E′, which passes through a transition range in a higher temperature side than the glass state range. Here, the change rate of the storage elastic modulus is maximized in the transition range. The crystal state is lost at intersection P at which the tangent line M₁ of the curve of the storage elastic modulus E′ passing through the glass state range intersects the tangent line M₂ of the curve of the storage elastic modulus E′ passing through the transition range, thereby starting the melting. As seen in FIG. 2, the artificial hair fiber of example 1 has the temperature at the intersection P within 180 to 240° C., and therefore can be processed with a commercially available hair iron (with a heating temperature of 240° C. or lower). In contrast, the artificial hair fiber of the comparative example 1 has the temperature at the intersection P higher than 240° C., and therefore it is not likely to be transformed by the heat of a commercially available hair iron.

INDUSTRIAL APPLICABILITY

The use of the artificial hair fiber of the present invention should not be limited, and the present invention is applicable to various hairpiece products for a headdress such as a wig, a hairpiece, a blade, and a hair extension, or for a doll's hair. 

1. An artificial hair fiber having a storage elastic modulus E′, wherein a ratio (E′₉₀/E′₁₅₀) of a storage elastic modulus E′ at a temperature of 90° C. to a storage elastic modulus E′ at a temperature of 150° C. is 3 to
 20. 2. The artificial hair fiber according to claim 1, wherein: a curve of the storage elastic modulus E′ includes a glass state range in which the storage elastic modulus E′ is constant and a transition range in which a change rate in the storage elastic modulus E′ becomes maximum, the transition range being on a higher temperature side than the glass state range; and a temperature coordinate of an intersection at which a tangent line of a curve of the storage elastic modulus E′ passing through the glass state range intersects a tangent line of a curve of the storage elastic modulus E′ passing through the transition range is located between 180 to 240° C.
 3. The artificial hair fiber according to claim 1, wherein said artificial hair fiber is made of a resin composition primarily consisting of one or both of thermoplastic polyester resin and thermoplastic polyimide resin.
 4. The artificial hair fiber according to claim 3, wherein: said artificial hair fiber is manufactured by melting and discharging the resin composition from a nozzle hole to produce an un-stretched yarn, and applying a stretching process to the un-stretched yarn, a ratio (D₁/D₂) of a stretch D₁ while the un-stretched yarn is produced after the resin composition is melted and discharged to a stretch D₂ during the stretching process is 1.5 to 14.0.
 5. A hairpiece product produced with the artificial hair fiber according to claim
 1. 6. The artificial hair fiber according to claim 2, wherein said artificial hair fiber is made of a resin composition primarily consisting of one or both of thermoplastic polyester resin and thermoplastic polyamide resin.
 7. The artificial hair fiber according to claim 6, wherein: said artificial hair fiber is manufactured by melting and discharging the resin composition from a nozzle hole to produce an un-stretched yarn, and applying a stretching process to the un-stretched yarn, a ratio (D₁/D₂) of a stretch D₁ while the un-stretched yarn is produced after the resin composition is melted and discharged to a stretch D₂ during the stretching process is 1.5 to 14.0.
 8. A hairpiece product produced with the artificial hair fiber according to claim
 2. 9. A hairpiece product produced with the artificial hair fiber according to claim
 3. 10. A hairpiece product produced with the artificial hair fiber according to claim
 6. 11. A hairpiece product produced with the artificial hair fiber according to claim
 4. 12. A hairpiece product produced with the artificial hair fiber according to claim
 7. 